The α-Globin and β-Globin Gene Families Are Found on Different

The α-globin and β-globin gene families are found on different chromosomes in humans. What is the suspected reason for this?

A) They evolved at different times.
B) There was a gene duplication event.
C) The α-globin originally coded for a different protein family.
D) Our ancestors didn't use the α-globin genes.
E) They were originally on the same chromosome but one set was moved via transposable elements.